The Petoskey Stone is actually a fossilized coral (Hexagonaria pericarnata) from a coral reef that existed in the northern Lower Peninsula during the Devonian era, 350 million years ago. The Petoskey Stone was adopted as the state stone by Public Act 89 of 1965.

The soft living tissue of the corallite was called polyp. At the center of the polyp was the food intake opening or mouth. This dark spot, or the eye of the corallite, has been filled with silt or mud that petrified after falling into the openings. Surrounding the opening were tentacles that were used for gathering food and drawing the food into the mouth. This living corallite thrived on plankton which lived in the warm sea.

Calcite, silica and other minerals have replaced the original elements in each cell. Each chamber or corallite at one time was a living marine animal that grew in colonies. The Petoskey stone is also known as a colony coral.

WHERE IS THE PETOSKEY STONE FOUND?

The Petoskey stone can be found in Michigan from the shores of Traverse City, north to the Charlevoix and Petoskey area, and across the state to Alpena.

Early spring is a good time to look for the stone after the ice has melted along the shore. Each year as the ice of Lake Michigan breaks up and the wind shifts the ice back and forth, it pushes a new crop of fossils to shore. During the summer months the best time to look for the stone is after a wind storm or during a mist rain when the stones will show the fossil pattern more clearly.

HOW DID THE PETOSKEY STONE GET ITS NAME?

The city of Petoskey was named after an Native American Ottawa Indian Chief, Chief Pet-O-Sega (Pet-O-Sega" means the "Rays of the Rising Sun). The eye of the stone is seen as the sun, and the lines or tentacles are seen as the rays radiating from the sun.

The stone was named Petoskey because of the abundance of them found along the shores of the Little Traverse Bay. In 1965 the State of Michigan adopted the Petoskey stone as Michigan's state stone.

HOW DO I IDENTIFY A PETOSKEY STONE?

Keeping in mind the scientific name, Hexagonaria, helps when looking for the stone. Its six sided pattern will allow you to identify it from other fossils. The pattern of the Petoskey stone fossil can be as little as 1/6 of an inch or larger. There are different grades of the stone from a porous soft stone to a very unique harder one. The stone can be found in many different variations from a whole Petoskey specimen to only a portion of the stone being "Petoskey". Being a fossil it is naturally soft and can have many imperfections such as cracks and other mineral deposits mixed in.

Petoskey stones found on the beachcan be smooth, and the fossil can be very distinct. This is not only because of the wave action of the water, but because the stones have been tumbled and rolled against other stones and smoothed by the sand. The pitted, rougher stones are usually found on shore or inland.

HOW DO I POLISH MY PETOSKEY STONE?

Polishing the Petoskey Stone at home is easily accomplished by using sand paper and steel wool. Begin with a relatively coarse grade of sand paper, graduating to finer grades. Smooth out sanding marks with very fine steel wool, and finish with leather or cloth soaked in oil. Do not use a rock tumbler, as the Petoskey stone is too soft and will be damaged.